Respiration sulfur

A heterotrophic sulfur respirer, Desulfuromonas acetoxidans, has been discovered which oxidizes acetic acid and ethanol with elemental sulfur to obtain energy for life processes (Pfennig and Biebl, 1976). 

Little is known about elemental sulfur reductase of the sulfur respiration system, though cytochrome c3 of the sulfate-reducing bacteria has been reported to reduce 

A sulfur reductase has been obtained from a heterotroph, Wolinella succinogenes (Schroder et al., 1988). This sulfur reductase has molecular mass of 200 kDa (made up of 85 kDa subunits) and an Fe/S cluster, but no heme. The enzyme catalyzes the oxidation of formate with elemental sulfur in the presence of formate dehydrogenase. As formate dehydrogenase used here has cytochrome b, the sulfur-reducing system of the bacterium is said to include cytochrome b. 

Flavocytochromes c from Chlorobium limicola f. thiosulfatophilum and Allo-chromatium (formerly Chromatium) vinosum have been reported to catalyze the reduction of elemental sulfur with strong reducing reagents such as benzyl viologen radical (Fukumori and Yamanaka, 1979 Yamanaka and Fukumori, 1980). 

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They occur in anaerobic sediments rich in sulfide and elemental sulfur, and live syntrophically with the phototrophic green sulfur bacteria (Chlorobi-aceae) that photooxidize H2S to S and excrete sulfur extracellularly. Desulfuromonas regenerate H2S by sulfur respiration, using, at least in part, organic matter leaked by Chlombium cells. 

From submarine hydrothermal vent environments, extremely thermophilic anaerobic archaea are capable of sulfur respiration with hydrogen gas ... 

SchauderR. and Kroeger A. (1993) Bacterial sulfur respiration. Arch. Microbiol. 159, 491-497. 

Fig. 1.12. A schematic presentation of the mechanisms which yield energy and biosynthesize organic compounds in the lithoautotrophic sulfur respiration...

The formation of methane by the methanogens is called carbon dioxide respiration, as described previously (p. 112). In general, cytochromes occur as the electron carrier in the respiration. Thus, some methanogens have cytochromes b and c. However, not all methanogens have cytochromes, as already mentioned. This may mean that carbon dioxide respiration is an early evolving stage of the respiration from the noncytochrome-type to the cytochrome-type. The electron transfer systems of the sulfur respirers contain cytochrome b or cytochromes b and c (Hedderich et al., 1999). In the iron respiration system of Pyrobaculum islandicum, cytochrome b seems to participate in the Fe(III) reducing system (Childers and Lovley, 2001). These results will show that the fundamental features of the respiration may have already been established in the hyperthermophilic chemolithoautotrophic archaea (Fig. 7.2). 

Poly sulfide Sulfur as an Intermediate in Sulfur Respiration 108... 

In this chapter, the polysulfide sulfur respiration of IV. succinogenes and other microorganisms will be described and the coupling mechanism of apparent proton translocation to polysulfide sulfur reduction will be discussed. Sulfur respiration involving also sulfate and sulfite [1-3,7] as well as the anaerobic respiration [3,7-10] with other acceptors have been reviewed previously. 

POLYSULFIDE SULFUR RESPIRATION OF BACTERIA 4.1. Bacterial Sulfur Reducers... 

WoUnella succinogenes grows by polysulfide sulfur respiration with either H2 [Reaction (6)] or formate [Reaction (7)] as electron donor [2,19]. Acetate and... 

Electron Transport Chain of Polysulfide Sulfur Respiration... 

The values of and Ap were nearly the same, since the ApH across the membrane was negligible. The H"7e and the ATP/e ratios were determined for fumarate respiration but not for polysulfide sulfur respiration. 

Table 2 Bioenergetic Data of the Polysulfide Sulfur Respiration with Formate of W. succinogenes [2], The Data are Compared to Those of Fumarate Respiration...

However, the values for polysulfide respiration can be estimated from the growth yields (Y) of W. succinogenes growing at the expense of Reactions (7) and (8). The growth yield of poly sulfide sulfur respiration was measured to be approximately half that of fumarate respiration, suggesting that the and... 

ATP/e ratio of polysulfide sulfur respiration was also half that of fumarate respiration [1]. This view is confirmed by the redox potential differences (AE) between formate and each of the two electron acceptors under the growth conditions of the bacteria. The AE of polysulfide sulfur respiration is approximately half that of fumarate respiration. The firee energy required for ATP synthesis calculated from AE and the ATP/e ratios are 116 and 127 kJ mol in anaerobic respiration with polysulfide sulfur and fumarate, respectively. Both values are consistent with the general observation that phosphorylation requires about 100 kJ moP ATP in growing bacteria in most instances. 

Figure 2 Composition of the electron transport chain catalyzing polysulHde sulfur respiration with H2 or formate in W. succinogenes. FdhA/B/C, formate dehydrogenase PsrA/B/C, polysulHde reductase HydA/B/C, hydrogenase Ni, nickel-iron center Fe/S, iron-sulfur centers Mo, molybdenum ion bound to MGD the dark squares designate heme b groups Sud, polysulfide sulfur transferase.

Table 3 Activities of Polysulfide Sulfur Respiration in Proteoliposomes Containing Different Naphthoquinones [6]...

Proteoliposomes containing polysulfide reductase and either hydrogenase or formate dehydrogenase isolated from W. succinogenes do not catalyze polysulfide sulfur respiration unless 8-methyl-menaquinone is present (Table 3). Menaquinone with a side chain consisting of six or four isoprene units, or vitamin Ki served in reconstituting fumarate respiration, but did not replace 8-methyl-menaquinone in polysulfide sulfur respiration. The low activities of polysulfide sulfur respiration observed without added 8-methyl-menaquinone were probably due to the small amounts of this quinone associated with the enzyme preparations used. Maximum activity of polysulfide sulfur respiration required 10 p.mol 8-methyl-menaquinone per gram phospholipid [O. Klimmek and W. Dietrich, unpublished results]. 

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